Exponential Attenuation

Setup:
The radium watch-hand was mounted on a small piece of wood, using glue. It was set up facing the
window of the GM-45, with a spacing of about half an inch.

Experiment:
The CPM were measured with nothing in the gap between the source and detector, as well as with varying
numbers of sheets of paper. Each reading was averaged for approximately 10 minutes, to help reduce
statistical variations.

Results:
Here is a table of the measured CPM vs the number of sheets of paper:

And here is a graph of the resulting data. The dark blue line is the data, the purple line is
an attempt at an exponential fit. The fit isn't perfect for several reasons, namely that
radium and daughter products emit several types of radiation, including several peak beta
energies, and the attenuation of beta sources is not purely exponential, due to energy softening
effects.

Thinking of buying a surplus CDV-700 or 715 detector? Be sure to read our
report
first.